Generally, silver halide color photographic materials have silver halide emulsion layers that are sensitive to the three primary colors, blue, green, and red, and they develop yellow, magenta, and cyan colors, respectively, thereby reproducing dye images by using the so-called subtractive color process. Therefore, the dye image that is reproduced is largely dependent on the color sensitivity of the layers and the spectral absorption properties of the developed colors.
Generally, these properties have not necessarily been as good as theoretically desired, because of restrictions with respect to color developability, etc., of the compounds that are used. Particularly, various improvements in the developed hue of magenta couplers, which is important in view of color reproduction, have been made. Among others, pyrazoloazole type magenta couplers are excellent in spectral absorption property of the developed hue.
For example, to improve the developed hue of magenta couplers, in the 5-pyrazolone type, anilino type magenta couplers more excellent in spectral absorption property than the ureido type and the acylamino type have been developed (see Japanese Patent Application (OPI) Nos. 74027/74 and 111631/74, etc., (the term "OPI" as used herein refers to a "published unexamined Japanese patent application"). Pyrazoloazole type magenta couplers that are low in undesired subabsorption have also been developed (see U.S. Pat. No. 3,725,067, etc.). In comparison to the colored images obtained from 5-pyrazolone type magenta couplers, the images obtained from this type of coupler are excellent in that undesired absorption in the blue light zone and the red light zone is less, which is favorable from the point of view of color reproduction, and yellowing is less probably because the coupler itself is stable to light, heat, and humidity, and hardly decomposes. On the other hand, in comparison to 5-pyrazolone type magenta couplers, the pyrazoloazole type magenta couplers have the drawback that when developed, the reaction of the oxidized product of the developing agent formed in the treating liquid with the couplers is apt to produce undesired magenta stain. This stain is conspicuous when the color developing bath contains a silver halide solvent such as a thioether.
To obviate the color fog that would tend to be formed by a color developing solution, several methods have been hitherto suggested.
It is said there are roughly three types of fog that are formed by a color developing bath. The first type of fog is due to the silver halide emulsion(s), the second type of fog is caused during storage from the formation of the photographic material to the developing treatment, and the third type of fog is due to couplers, which develop colors indiscriminately with the oxidized product of a developing agent that is present in a small amount in the developing solution. To prevent these types of fog, it is known to use, for example, compounds having a mercapto group and tetraazaindenes, which is disclosed in U.S. Pat. Nos. 3,954,474, 3,982,947 and 4,021,248, Japanese Patent Publication No. 28660/77, Research Disclosure, RD No. 17643, etc.
On the other hand, to prevent color fog, it is known that hydroquinone derivatives are effective. For example, with respect to di-branched alkylhydroquinones, reference can be made to U.S. Pat. Nos. 3,700,453 and 2,732,300, with respect to di-linear alkylhydroquinones, reference can be made to U.S. Pat. Nos. 2,728,659 and 2,732,300, with respect to mono-branched alkylhydroquinones, reference can be made to U.S. Pat. No. 3,700,453, with reference to mono-linear alkylhydroquinones, reference can be made to U.S. Pat. No. 2,728,659, and with respect to other hydroquinone derivatives, reference can be made to U.S. Pat. Nos. 2,360,290, 2,701,197, 2,336,327, 2,403,721, 3,582,333, etc.
However, it has been found that although compounds having a mercapto group or tetraazaindenes can reduce fog somewhat, they are not effective enough against color fog, and although hydroquinone derivatives that are conventionally used are very effective in reducing color fog, they damage the dye stability of pyrazoloazole type couplers against light.